X-ray diffraction, neutron diffraction and electron diffraction are commonly used to determine crystal structures of samples. Herein, x-ray diffraction is useful in analyzing single crystals of sizes down to some μm, whereas electron beam diffraction can be applied to even smaller crystal sizes since an electron beam probe may have a very low diameter and due to a higher scattering cross section of electrons. The higher scattering cross section of electrons also results in multiple scattering of the electrons in the sample such that both desired single scattering events and undesired multiple scattering events are recorded in a scattering image. A method known as precession diffraction can be used to reduce the amount of multiple scattering events relative to single scattering events in a recorded scattering image such that a crystal structure of a measured sample can be derived from such image with a higher accuracy.
In precession diffraction, a deflection system upstream of a sample in a transmission electron microscope is used to tilt an incident beam such that it rotates about its location of incidence on the sample. A second deflection system downstream of the sample and upstream of a detector compensates the rotating tilt of the incident beam such that a stable diffraction pattern can be recorded on the detector. This recorded diffraction pattern is better suited to derive a crystal structure of the sample than a corresponding pattern recorded without the rotating tilt of the incident beam.